i have a 1987 f150,it has a 302,fi.b 4x4. i bought it about a month ago, it was getting about 10mpg, i recently gave it a tune up to try to improve my fuel economy,i went about 30 or 40 miles and lost about 11 gallons of fuel, there is no puddle of gas, but i do smell fuel by the front tank,also, some one has torn into the poor truck and its obvious they had no idea what they were doing.any ideas on the fuel problem?im going to tear into it today and trace all the fuel lines down

 

Are your sending units working properly? Fuel might be returning to the front tank (fuel reservoir issue).

 

my fuel gauge works intermittently. its not dumping fuel into the rear tank nor is it running rich.i did smell gas by the front tank but no drips or puddles.im going to run it and crawl underneath it. hopefully i can find the leak without dropping the tank or removing the bed.also theres stray vacuum lines not connected to anything

 

i ran the truck, not a drip anywhere.the gas smell is coming from the filler tube.no fuel in the back tank either,its bone drytheres an red vacuum line that come off a cluster of modules by the coil that has a golf tee in it, also theres an orange vacuum line that comes off a junction on the plenum,it runs to a canister that has a red and black vacuum line plugged in to it.if any one here can shoot me some pics of vacuum diagrams.i t would be most helpful.its an 87 f150,302,4x4 with air.i also bought a new serpentine belt and it was way to small.im thinking the idler pulley is off a different engine